chore(manifest): update MANIFEST.in to include backend files and exclude frontend and cache directories

MANIFEST.in

@@ -1,3 +1,12 @@
 recursive-include meshchatx/public *
-recursive-include meshchatx/src *
+recursive-include meshchatx/src/backend *
+include meshchatx/src/version.py
+include meshchatx/src/__init__.py
+include meshchatx/meshchat.py
+include meshchatx/__init__.py
+
+exclude meshchatx/src/frontend
+recursive-exclude meshchatx/src/frontend *
+recursive-exclude * __pycache__
+recursive-exclude * *.py[co]